The role of complementarity and facilitation in influencing tree community resilience

全球变化因素，如昆虫和病原体的外来入侵以及气候变化，正在对世界上许多地区许多树种的生长和生存以及许多森林生态系统的功能产生负面影响。目前的研究表明，混合树种可以更好地应对压力环境事件。然而，在什么类型的林分和环境条件下使用什么类型的混合物以最大限度地提高森林对自然和人为引起的压力源的恢复能力，这在很大程度上是未知的。在这个发现研究项目中，我打算测试几个假设，关于森林的组成和结构如何与基本共存机制相互作用，以促进（或不促进）树木和森林对许多不同的永久和/或间歇性压力源单独或共同作用的抵抗力和恢复（两种恢复力的测量）。我将使用控制的实地实验和在管理和非管理的森林中设置的永久地块来调查这些问题。我将与研究生和博士后密切合作，并与来自世界各地的科学家合作来回答这些问题。

Global change factors such as non-native invasion of insects and pathogens as well as climate change are negatively affecting the growth and survival of many tree species and functioning of many forest ecosystems in a great number of regions in the world. Current studies indicate that mixtures of tree species can better cope with stressful environmental events. However, what types of mixtures to use under what types of stand and environmental conditions to maximise forest resilience to natural and human-induced stressors are mostly unknown. In this discovery research program, I intend to test several hypotheses regarding how forest composition and structure are interacting with basic coexistence mechanisms to promote (or not) both tree and forest resistance and recovery (both measures of resilience) to many different permanent and/or intermittent stressors acting alone or in conjunction. I will use a combination of controlled field experiments and permanent plots set in managed and unmanaged forests to investigate these questions. I will work closely with graduate students and Post-Docs and collaborate with scientists from around the world to answer these questions. An ambitious new field experiment where various mixtures of tree species grown in different densities and spatial arrangements is currently being established near Ripon in Quebec, Canada, to test some of these hypotheses in a controlled setting. Data from more than 25 international tree-diversity experiments will also be used to test how tree diversity affects forest resilience to various stressors in a wide set of climatic conditions and tree species mixtures. Small and large scale permanent plots established in managed and natural forests in a wide range of environmental conditions from more than 60 countries will be used to increase the practical relevance of our findings and to test the generality of our findings. The growth and mortality at the tree and plot scales will be studied in relation to known recent climatic and biotic stressors that have occurred. The results of this study will be used to design novel management approaches for increasing the resilience and survival of trees facing global change from urban parks and gardens, agricultural crops, and managed forests to vast protected areas of forested land. A better understanding of the benefits of maintaining or increasing tree diversity and stand complexity opens up many possible applications as we face the increasing challenge of managing and restoring increasingly novel and stressed ecosystems.